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It seems obvious that fasting will lead to weight loss, but at one time it was not thought to be the best way to do it. Experts told us that our bodies would go into ‘starvation’ mode and our metabolic rate would slow down, so we would use less energy and hence need less food. It was therefore thought to be better to eat plenty of small meals to keep the metabolic ‘fire’ stoked up. But research in animals and humans now seems to show that this is not the case.
We are adapted to fasting
If practiced intermittently (which you will hear more of later) fasting has been shown not to slow metabolism, and it turns out that we are well-adapted to it.
In prehistoric times food was not always readily available and we generally alternated between times of feast or famine.
Is fasting actually good for us?
Yes, in more ways than one. The more we eat, particularly sugary or high carbohydrate food, the more of the hormone, insulin, our bodies have to produce. As well as reducing the level of sugar in the blood (by ‘pushing’ it into cells where it is used as energy), insulin also makes us store spare glucose as fat. So the more we eat, the more fat we store – I think many of us have witnessed this effect!
Fasting and insulin sensitivity
But when we fast our insulin levels go right down and our cells become more sensitive to it, so that when we eat we store less of the glucose as fat. Maintaining the sensitivity of our cells to insulin will also help to prevent type 2 diabetes developing (look out for the article with more on this).
How long does a fast last?
Differing durations of fasting have been researched and recommended by various people. Prolonged fasts (more than a few days) will result in loss of muscle as well as fat, which will just be put back on when you eat again. Some people recommend four-day fasts but most of us would find that too long to repeat on a regular basis.